Semiconductor device and lead frame used therefor

ABSTRACT

A semiconductor device in which a semiconductor chip, a lead frame and metal wires for electrically connecting the lead frame are sealed with sealing resin. The lead frame has a plurality of lead terminal portions, a supporting portion for supporting the semiconductor chip, and hanging lead portions supporting the supporting portion. Each of the lead terminal portions adjacent to the hanging lead portion is a chamfered lead terminal portion having, at its head, a chamfered portion formed substantially in parallel with the hanging lead portion so as to avoid interference with the hanging lead portion.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a resin-sealed typesemiconductor device, and especially to a one-side resin-sealed typesemiconductor device in which a surface of a lead frame on which asemiconductor element is mounted is sealed with a resin and a lead frameused therefor.

[0003] 2. Description of Related Art

[0004] Resin-sealed type semiconductor devices each provided with a leadframe for electrically connecting electrodes of the semiconductor to anouter wiring and the like are widely used. In such a semiconductordevice, a lead frame generally comprises a supporting portion formounting a semiconductor element thereon, hanging lead portions forsupporting the supporting portion, and lead terminal portions forconnecting metal wires thereto. A lead frame used in the process offabricating semiconductors includes a plurality of unit regionscorresponding to a plurality of semiconductor devices so that theplurality of semiconductor devices can be fabricated at the same time.One unit region has a substantially rectangular shape. Each of thehanging lead portions extends inwardly from a corner portion of thisrectangle, and in many cases, the lead terminal portions extend inwardlyfrom side parts of the unit region.

[0005]FIG. 5 is an enlarged schematic pan view showing a part in thevicinity of a corner of a unit region.

[0006] In the central part of the substantially rectangular unit region(in the direction of arrow G), a supporting portion 51 is disposed. Ahanging lead portion 52 extends from the supporting portion 51 towardthe corner portion. In the side parts of the unit region, substantiallyrectangular lead terminal portions 53 are provided. Base end portions ofthe lead terminal portions 53 are connected to a peripheral frame part50. The longitudinal direction of the hanging lead portion 52 and thelongitudinal direction of the lead terminal portion 53 makes an angle ofsubstantially 45°.

[0007] In a lead frame, a plurality of unit regions each having such astructure are arranged and connected to the frame part 50. In theprocess of fabricating semiconductor devices, a lead frame is sealedwith a sealing resin in such a manner that the bottom surface of thelead terminal portion 53 is exposed. Thereafter, each unit of lead frameis cut along a cutting line M shown in broken line, and the cut end faceis substantially in the same plane with the side surface of the sealingresin.

[0008] In order to obtain a small-sized semiconductor device, it ispreferable that the length of the lead terminal portion 53 is as shortas possible. However, since the lead terminal portion 53 functions as alead for connection with outer wiring substrate, the lead terminalportion 53 needs to have a length (area) more than a predeterminedlength (area). From these reasons, the lead terminal portion 53 isformed to have a predetermined necessary minimum length L1.

[0009] The minimum distance between the hanging lead portion 53 and thelead terminal portion 53A adjacent to the hanging lead portion 53 mustbe large enough to ensure insulating reliability between them. However,in order to obtain a small-sized semiconductor device, it is preferablethat the minimum distance between them is small. From these reasons, theminimum distance between them is designed to be a predeterminednecessary minimum distance L2.

[0010] However, since the predetermined length L1 and the predeterminedistance L2 are required to be secured, miniaturization of mounting areaof a semiconductor device is limited.

SUMMARY OF THE INVENTION

[0011] An object of the present invention is to provide a semiconductordevice in which each lead terminal portion has a length (area) necessaryfor outer connection and at has a length (area) necessary for outerconnection and at the same time insulating reliability between thehanging lead portions and lead terminal portions is secured, and a leadframe used for the semiconductor device.

[0012] Another object of the present invention is to provide asemiconductor device having a small mounting area, and a lead frame usedfor the semiconductor device.

[0013] A semiconductor device according to the present inventioncomprises a semiconductor chip having electrodes on the surface thereof,a lead frame having a plurality of lead terminal portions for electricconnection and a plurality of hanging lead portions each extendingobliquely with respect to the lead terminal portions and supporting asupporting portion on which the semiconductor chip is mounted, metalwires for connecting the lead terminal portions and the electrodes ofthe semiconductor device, and a sealing resin for sealing thesemiconductor element, the lead frame and the metal wires in such amanner that a part of each lead terminal portion is exposed. Theplurality of lead terminal portions include chamfered lead terminalportions each having, at its head, a chamfered portion formedsubstantially in parallel with the hanging lead portion so as to avoidinterference with the hanging lead portion.

[0014] Further, a lead frame according to the present inventioncomprises a plurality of lead terminal portions for electric connectionand a plurality of hanging lead portions each extending obliquely withrespect to the lead terminal portions and supporting a supportingportion on which the semiconductor chip is mounted. The plurality oflead terminal portions include chamfered lead terminal portions eachhaving, at its head, a chamfered portion formed substantially inparallel with the hanging lead portion so as to avoid interference withthe hanging lead portion.

[0015] According to this invention, the lead terminal portions arechamfered substantially in parallel with the hanging lead portion so asto avoid interference with the hanging lead portions. Accordingly, evenif the chamfered lead terminal portion is disposed nearer to the hanginglead portion in comparison with the case of the conventional leadterminal portion, a distance more than a predetermined distance canstill be secured between the lead terminal portion and the hanging leadportion.

[0016] That is, in a conventional lead frame, a lead terminal portionhas a corner portion protruding toward a hanging lead portion.Therefore, it has been necessary to dispose the lead terminal portionsubstantially on the peripheral part side in order to avoid interferencebetween an edge of the corner portion and the hanging lead portion andsecure a distance more than a predetermined value therebetween. As aresult, a unit region in a lead frame corresponding to a semiconductorbecomes large, and the size in the plane direction of a semiconductordevice using this unit region becomes large.

[0017] On the contrary, according to the present invention, the leadterminal portion has a chamfered portion at its head and is opposed tothe hanging lead portion at this chamfered portion. Therefore, thehanging lead portion can be disposed at a more inner portion incomparison with the case of the conventional structure. Accordingly, aunit region of lead frame can be small-sized. As a result, the size inthe plane direction of a semiconductor device can be reduced and themounting area of the same can be also reduced.

[0018] The chamfered portion is preferably comprises a linear side (Cchamfering side) in parallel with the lateral side of the hanging leadportion. However, other shapes are similarly effective as long as theportion is chamfered so as to avoid interference by the hanging leadportion. For example, the chamfered portion may comprise a curved side(for example, R chamfering side). Further, in the chamfered portion, theoblique side may extend through only a part or the whole width of thelead terminal portion.

[0019] It is preferable that the abovementioned chamfered lead terminalportion is disposed adjacent to the hanging lead portion.

[0020] Not only the lead terminal portion adjacent to the hanging leadportion but also another lead terminal portion adjacent to thischamfered lead terminal portion may be a chamfered lead terminalportion. However, in this case, the chamfered lead terminal portionadjacent to the hanging lead portion becomes shorter than the otherchamfered lead terminal portions. Therefore, it is preferable that onlylead terminal portions adjacent to the hanging lead portion have such achamfered portion. In this case, there is no remarkably short leadterminal portion. Therefore, in a semiconductor device using such a leadframe, all the lead terminal portions can be suitably connected to metalwires and an outer wiring substrate.

[0021] When only each lead terminal portion adjacent to the hanging leadportion comprises a chamfered lead terminal portion, the chamferedportion preferably has an oblique side extending throughout the wholewidth of the lead terminal portion. Thereby a unit region of lead framecan be minimized and the size of a semiconductor device using the samecan be minimized in plan view.

[0022] The foregoing and other objects, features, aspects and advantagesof the present invention will become more apparent from the followingdetailed description of the present invention when taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023]FIG. 1 is a schematic plan view showing a unit region of leadframe according to an embodiment of the present invention.

[0024]FIG. 2 is an enlarged schematic plan view showing a part in thevicinity of a corner of the unit region of lead frame shown in FIG. 1.

[0025]FIG. 3A is a sectional view along a cutting line C-C in FIG. 2,and

[0026]FIG. 3B is a sectional view along a cutting line D-D in FIG. 2.

[0027]FIG. 4 is a schematic sectional view of a resin-sealed typesemiconductor device fabricated using the lead frame shown in FIG. 1.

[0028]FIG. 5 is an enlarged schematic plan view showing a part in thevicinity of a corner of a conventional lead frame.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029]FIG. 1 is a schematic plan view showing a unit region (arepetition unit corresponding to a semiconductor device) of a lead frame1 according to an embodiment of the present invention. The unit regionof the lead frame 1 is, for example, substantially in the shape of asquare and substantially symmetrical in the vertical and horizontaldirections in FIG. 1. Therefore, reference numerals are given to onlythe upper left quarter part of the unit region in FIG. 1, but each ofthe remaining quarter parts has the same shape. The unit regioncomprises a frame portion 2 disposed in the peripheral part, asupporting portion 4 in the central part, a hanging lead portion 3connecting the supporting portion 4 and an inner corner portion of theframe portion 2, and lead terminal portions 5 disposed on the inner sideof the frame portion 2. The frame portion 2 is usually provided withholes (not shown) for positioning, fixing and the like the lead frame 1in the fabricating process of a semiconductor device.

[0030] The supporting portion 4 extends diagonally from the inner cornerof the frame portion 2 through the hanging lead portion 3. In otherwords, the whole of the supporting portion 4 is X-shaped. The supportingportion 4 is larger in width than the hanging lead portion 3. A step isprovided in the way of the hanging lead portion 3, and the supportingportion 4 is upset in a higher position than that of the frame portion2.

[0031] The lead terminal portions 5 extend from the inner sides of theframe portion 2 toward the center thereof and vertically with respect tothe inner sides. The hanging lead portion 3 is oblique with respect tothe longitudinal direction of the lead terminal portions 5 with an angleof about 45° in plan view. Each of the lead terminal portions 5 has thesame length.

[0032] A plurality of such unit regions each having the abovementionedstructure are disposed in close to one another and constitute a leadframe.

[0033] In the process of fabricating a semiconductor device, asemiconductor chip is die-bonded on the supporting portion 4, andelectrodes of the semiconductor chip and the lead terminal portions 5are connected to each other by metal wires. Thereafter, thesemiconductor chip, the supporting portion 4, a part of the hanging leadportion 3 and a part of the lead terminal portions 5 are covered with asealing resin and the lead terminal portions 5 and the hanging leadportions 3 are cut at the position of a cutting line E shown in a brokenline. The region covered with the sealing resin is a region enclosed bythe cutting line E.

[0034]FIG. 2 is an enlarged schematic plan view showing a corner part ofa unit region of lead frame shown in FIG. 1.

[0035] Among the plurality of lead terminal portions 5, each leadterminal portion 5B not adjacent to the hanging lead portion 3 has ahead side formed perpendicular to the length thereof. On the other hand,each lead terminal portion 5A adjacent to the hanging lead portion 3 hasan oblique head side substantially in parallel with and opposed to thesides of the hanging lead portion 3 through the whole width of the leadterminal portion 5A. In other words, the lead terminal portion 5A is achamfered lead terminal portion having, at its head end, a chamferedportion formed substantially in parallel with the hanging lead portion 3so as to avoid interference with the hanging lead portion 3.

[0036] Step portions are provided at the sides of each lead terminalportion 5. That is, the lead terminal portion 5 has two wide portionsand two narrow portions alternately disposed at shifted positions in thelongitudinal direction thereof. The two wide portions and one narrowportion are wholly sealed within the sealing resin, and the remainingnarrow portion is partly sealed with the sealing resin. With such ashape, the lead terminal portion 5 is hard to be pulled out toward theperipheral side.

[0037]FIG. 3A is a sectional view along the cutting line C-C of FIG. 2and FIG. 3B is a sectional view along the cutting line D-D of FIG. 2.

[0038] The section along the cutting line C-C is a section of the wideportion of the lead terminal portion 5, and is in the shape of aninverted trapezoid the upper side of which has a length t1 and the lowerside of which has a length t2 (t1>t2) (FIG. 3A).

[0039] The section along the cutting line D-D is a section of the narrowportion of the lead terminal portion 5, and is in the shape of arectangle having a width t2 (FIG. 3B). That is, the upper surface of thelead terminal portion 5 has different two widths t1 and t2 shifted inthe longitudinal direction, but the bottom surface thereof has the fixedwidth t2.

[0040] After sealing the lead frame 1 with a sealing resin, the sealingresin is filled to the position F in the same plane with the bottomsurface of the lead terminal portion 5, and the bottom surface of thelead terminal portion 5 is exposed from the sealing resin to form aterminal portion for outer connection (an outer lead portion). At thewide portion having an inverted trapezoidal section (FIG. 3A), the leadterminal portion 5 is wider in the sealing resin and has taperedsurfaces opposed to the bottom surface side of the sealing resin. Withthis structure, the lead terminal portion 5 is hard to be pulled outdownwardly from the sealing resin.

[0041] Further description will be given with reference to FIG. 2 again.

[0042] Since the lead terminal portion 5 functions as a lead forconnection with outer wiring substrate, the exposed area of the leadterminal portion 5 from the sealing resin must be lager than apredetermined area. Therefore, it is necessary to secure more than apredetermined length of the lead terminal portion 5 after being cut. Onthe other hand, in order to obtain a small-sized semiconductor device,it is preferable that the length of the lead terminal portion 5 is asshort as possible. From these reasons, the lead terminal portion 5 isformed to have a predetermined necessary minimum length L1.

[0043] The minimum distance between the hanging lead portion 3 and thelead terminal portion 5A adjacent to the hanging lead portion 3 must belarge enough to ensure insulating reliability between them. However, inorder to obtain a small-sized semiconductor device, it is preferablethat the minimum distance between them is small. From these reasons, theminimum distance between them is designed to be a predeterminednecessary minimum distance L2.

[0044] When, using a lead terminal portion 53 having a conventionalshape shown in FIG. 5, the length of the lead terminal portion 53 is setto be the predetermined length L1 and the minimum distance between thehanging lead portion 52 and the adjacent lead terminal portion 53 is setto be the predetermined distance L2, the lead terminal portion 53 mustbe disposed further on the peripheral portion side in comparison withthe case of this embodiment. The reason is that, since a corner portion54 of a conventional lead terminal portion 53 at the most adjacentposition to the hanging lead portion 52 protrudes toward the hanginglead portion 52, the minimum distance becomes smaller than thepredetermined distance L2 when the head end position A1 is aligned withthe head end position B1 of this embodiment. Therefore, the head endposition B1 of the lead terminal portion 5 of this embodiment can be setat a more inner position by a distance L3 in comparison with the headend position A1 of the conventional lead terminal portion 53. Since thelengths of the lead terminal portions 5, 53 are the predetermined lengthL1 respectively, the rear end position B2 of the lead terminal portion 5of this embodiment is at a more inner position in comparison with therear end position A2 of the conventional lead terminal portion 53. As aresult, a unit region of such a lead frame 1 according to the presentinvention can be small-sized.

[0045] Further, since the sealing resin is formed substantially in thesame plane with the rear end positions A2, B2, a semiconductor deviceusing a lead frame 1 of this embodiment can be more small-sized by 2×L3per one side. Therefore, the packaging area of the semiconductor devicecan be smaller.

[0046]FIG. 4 is a schematic sectional view of a semiconductor devicefabricated using such a lead frame 1. Each part of the lead frame 1 isgiven with the same reference numeral as shown in FIG. 1 and thedescription thereof is omitted.

[0047] A semiconductor chip 6 is die-bonded on a supporting portion 4.The supporting portion 4 is X-shaped (see FIG. 1). The area of the uppersurface of the supporting portion 4 is smaller than that of the bottomsurface of the semiconductor chip 6.

[0048] Electrodes formed on the upper surface of the semiconductor chip6 and the lead terminal portions 5 are electrically connected to eachother by metal wires 7. The semiconductor chip 6, metal wires 7 and apart of the lead frame 1 are covered with a sealing resin 8. At thebottom surface of the semiconductor device, the lead terminal portions 5and the sealing resin 8 are formed in the same plane, and the bottomsurface of each lead terminal portion 5 is exposed. The sealing resin 8is present below the supporting portion 4 by a thickness correspondingto the height of the upsetting. Further, the end face of the leadterminal portion 5 is substantially in the same plane with the sidesurface of the sealing resin 8.

[0049] A semiconductor device having such a structure can besurface-mounted, for example, on a wiring substrate with the leadterminal portions 5 exposed at the bottom surface functioning as outerterminals. Further, since only one surface side of the lead terminalportion 5 is sealed by the sealing resin 8, the thickness of thesemiconductor device can be made smaller. Therefore, such asemiconductor device can be suitably mounted on each kind of thin typeapparatus.

[0050] The sealing resin 8 is present below the supporting portion 4,and therefore, the supporting portion 4 and the hanging lead portion 3are firmly connected with the sealing resin 8. Since the area of thesupporting potion 4 is smaller than that of the bottom surface of thesemiconductor chip 6, parts of the bottom surface of the semiconductorchip 6 are in direct contact with the sealing resin 8. As a result,exfoliating phenomenon occurring at the boundary surface between thesupporting portion 4 and the semiconductor element 6 can be reduced.

[0051] Though one embodiment of the present invention has been describedabove, the present invention can be embodied in other forms. Forexample, in the abovementioned embodiment, a lead terminal portion 5having the wide portions and the narrow portions, but the lead terminalportion 5 may have the same width throughout the length thereof.Further, the wide portion of the lead terminal portion 5 has a sectionin the shape of an inverted trapezoid in the abovementioned embodiment,but the wide portion may have a rectangular section. Further, the narrowportion of the lead terminal portion 5 may have a section in the shapeof an inverted trapezoid, and the lead terminal portion 5 may have thesame section in the shape of an inverted trapezoid throughout the lengththereof.

[0052] Further, in the abovementioned embodiment, the head end face ofthe lead terminal portion 5 is in the same plane with the side surfaceof the sealing resin 8, but the head end face of the lead terminalportion 5 may covered with the sealing resin 8. Furthermore, the leadterminal portion 5 may be cut at a position protruding from the sealingresin 8. In this case, since the lead terminal portion 5 can be mountedon a wiring substrate or the like at a position protruding from thesealing resin 8, the lower surface of the lead terminal portion 5 neednot be exposed from the sealing resin 8.

[0053] Further, though the supporting portion 4 on which a semiconductorchip 6 is die-bonded is X-shaped in the abovementioned embodiment, thesupporting portion 4 may be in other shapes such as a rectangle.

[0054] Further, though the supporting portion 4 is upset in theabovementioned embodiment, the present invention can include suchstructures that the supporting portion 4 is in the same plane with thelead terminal portion 5 and that the supporting portion 4 is downset ata position lower than the lead terminal portion 5.

[0055] Although the embodiments of the present invention has beendescribed and illustrated in detail, it is clearly understood that thesame is by way of illustration and example only and is not to be takenby way of limitation, the spirit and scope of the present inventionbeing limited only by the terms of the appended claims.

[0056] This application corresponds to the Japanese Patent ApplicationNo.2000-307377 filed in the Japanese Patent Office on Oct. 6, 2000, andthe entire disclosure of the Japanese application is incorporated hereinby reference.

What is claimed is:
 1. A semiconductor device comprising a semiconductorchip having electrodes on the surface thereof, a lead frame having aplurality of lead terminal portions for electric connection and hanginglead portions each extending obliquely with respect to the lead terminalportions and supporting a supporting portion on which the semiconductorchip is mounted, metal wires for connecting the lead terminal portionsand the electrodes of the semiconductor chip to each other, and asealing resin for sealing the semiconductor chip, the lead frame and themetal wires in such a manner that a part of each lead terminal portionis exposed, the plurality of lead terminal portions including chamferedlead terminal portions each having, at its head end, a chamfered portionformed substantially in parallel with the hanging lead portion so as toavoid interference with the hanging lead portion.
 2. A semiconductordevice as claimed in claim 1, in which the chamfered lead terminalportion is disposed adjacent to the hanging lead portion.
 3. Asemiconductor device as claimed in claim 1, in which the chamfered leadterminal portion has an oblique side extending throughout a whole widthof the chamfered lead terminal portion.
 4. A semiconductor device asclaimed in claim 1, in which an end face of the lead terminal portion issubstantially in a same plane with a side surface of the sealing resin.5. A semiconductor device as claimed in claim 1, in which a bottomsurface of the lead terminal portion is exposed from a bottom surface ofthe sealing resin to form an outer lead portion.
 6. A semiconductordevice as claimed in claim 1, in which the lead terminal portion has awide portion and a narrow portion at shifted positions in a longitudinaldirection thereof.
 7. A semiconductor device as claimed in claim 1, inwhich at least a part of a section of the lead terminal portion is in ashape of an inverted trapezoid.
 8. A lead frame comprising a pluralityof lead terminal portions for electric connection, and a plurality ofhanging lead portions each extending obliquely with respect to the leadterminal portions and supporting a supporting portion on which asemiconductor chip is mounted, the plurality of lead terminal portionsincluding chamfered lead terminal portions each having, at its head end,a chamfered portion formed substantially in parallel with the hanginglead portion so as to avoid interference with the hanging lead portion.9. A lead frame as claimed in claim 8, in which the chamfered leadterminal portion is disposed adjacent to the hanging lead portion.
 10. Alead frame as claimed in claim 8, in which the chamfered lead terminalportion has an oblique side extending substantially throughout a wholewidth thereof.
 11. A lead frame as claimed in claim 8, in which the leadterminal portion has a wide portion and a narrow portion at shiftedpositions in a longitudinal direction thereof.
 12. A lead frame asclaimed in claim 8, in which at least a part of a section of the leadterminal portion is in a shape of an inverted trapezoid.